Problem: $ {-9\cdot \left[ \begin{array}{cc} 4 \\ -1 \\ 4 \end{array} \right]=}$
Explanation: The Strategy To multiply a matrix by a scalar, we multiply each term of the matrix by the scalar. Multiplying each term $ {\begin{aligned}-9\cdot \left[\begin{array}{rr} {4} \\ {-1} \\ {4} \end{array}\right]&=\left[\begin{array}{rr} -9\cdot{4} \\ -9\cdot{-1} \\ -9\cdot{4} \end{array}\right] \\\\&=\left[\begin{array}{rr} {-36} \\ {9} \\ {-36} \end{array}\right]\end{aligned}}$ Summary $ {-9\cdot \left[ \begin{array}{cc} 4 \\ -1 \\ 4 \end{array} \right]=\left[ \begin{array}{cc} -36 \\ 9 \\ -36 \end{array} \right]}$